Individualized humeral tray selection in a single design of implant (comprehensive system; Zimmer Biomet, Warsaw, IN) based on clinical symptoms and anatomy enhanced clinical outcomes following reverse total shoulder arthroplasty

Background

Recently, a medialized offset eccentric humeral tray was introduced to overcome the complications based on excessive humeral lateralization after reverse total shoulder arthroplasty (rTSA). However, previous literature evaluating the clinical outcomes of the eccentric tray is still not sufficient. Therefore, this study aimed to compare the functional outcomes of rTSA according to individualized humeral tray selection based on clinical symptoms and anatomical parameters. We hypothesized that rTSA with individualized tray selection would result in better clinical outcomes than the routine use of a concentric or eccentric tray regardless of clinical or radiological findings.

Methods

We retrospectively reviewed 182 patients who underwent rTSA with a single type of lateralized glenoid–lateralized humerus implant with adjustable tray options (Comprehensive System; Zimmer Biomet, Warsaw, IN, USA) between September 2017 and March 2022. Since the eccentric tray became available for use in December 2019, patients before (early period) and after this date (late period) were divided into four groups based on the study period and humeral tray options; Groups EE (early period, indicated for eccentric tray but not applied), EC, LE (late period, eccentric tray), and LC (late period, concentric tray). The eccentric tray was indicated to overcome pseudoparalysis, meanwhile, the concentric tray was utilized in patients with positive external rotation lag sign without pseudoparalysis. If a patient had neither pseudoparalysis nor external rotation lag sign, the eccentric tray was utilized in patients with a critical shoulder angle less than 32° or center of rotation–to–acromion distance more than 14 mm. Functional and radiological outcomes were compared between four groups. The mean follow-up duration for the overall cohort was 12.8 ± 2.0 months (range: 12-24).

Results

Compared to EE, LE presented greater distalization (EE vs. LE 29.0 ± 5.0 mm vs. 38.0 ± 4.0 mm, P < .001) and less lateralization (19.0 ± 5.0 mm vs. 15.0 ± 4.0 mm, P = .001). Also, LE showed better postoperative forward flexion than EE (134.3° ± 14.1° vs. 144.2° ± 8.8°, P < .001). Meanwhile, the functional and radiological outcomes of LC were not different from those of EC (all P > .05). Notably, subacromial erosion was observed in EE alone (5.4%, 2/37).

Conclusion

To achieve favorable outcomes and avoid postoperative complications, the mediolateral offset of the humeral tray for lateralized rTSA should be selected based on a comprehensive consideration of clinical symptoms and anatomical characteristics of individual patients.